Treating cracked petroleum distillates for color



Patented June 24, 1941 rs'r FFlCE TREATIN G CRACKED PETROLEUM DISTILLATES FOR COLOR Robert E. Burk, Cleveland Heights, Ohio, assignor to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application December 24, 1938, Serial No. 247,719

Claims.

It has been suggested to desulphurize sulphurcontaining petroleum distillates by reacting with the sulphur compounds by means of iron carbonyl, iron compounds being formed with the sulphur constituents. I have now found that cracked petroleum distillates, if treated with small amounts of iron carbonyl, insufiicient for desulphurizing, and with provision of proper temperature conditions, show a surprising action in lightening the color and eliminating gum. This is all the more remarkable, in View of the fact that it would be expected that iron compounds would inherently tend to make the color worse.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described, and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative however, of but a few of the various ways in which the principle of the invention may be employed.

The cracked petroleum distillate is treated by supplying thereto a small amount of iron carbonyl, insufficient for desulphurization, and the distillate is subjected to an elevated temperature. Suitably, the temperature will be above that of steam, and while the desired action may be had even up in a higher range short of serious decomposition of the distillate, it is particularly convenient to operate in such temperature conditions as four hundred to seven hundred degrees Fahrenheit. Very advantageously, a distillate having light and heavy components is treated, and the lighter components are separated in the course of the procedure. Thus, conveniently, in a cracking plant in which the cracked products able to vaporize are taken to fractionating zones involving a first and a second fractionating column or tower, effective procedure may be had by introducing the iron carbonyl into the upper portion of the first tower. The action goes on with the hydrocarbons in process of separation, the temperature being on the order of four hundred fifty to six hundred fifty degrees Fahrenheit, and the light fraction or gasoline is thence taken off.

{The distillate thus may be subjected to a suitable temperature, as indicated, the carbonyl being provided. It is advantageous to estimate the sulphur content of the material being operated upon, and this may be determined to whatever degree of precision may be desired, and account may be taken of the mercaptan sulphur as such and, where appropriate, determination also of hydrogen sulphide as such. The amount of carbonyl employed is taken less than what would correspond to the amount required to react with such mercaptan sulphur, or total sulphur, according to particular conditions, and the treatment then proceeds, acting on the constituents occasioning gum and color without reacting out the sulphur content; and whereas in the reacting to take out the sulphur the latter combines with the metal of the carbonyl, Where dealing with organic constituents which tend to polymerize to coloring substances and gum the metal is immaterial and merely a carrier of the rest of the molecule. The distillates treated may be any of those subject to dificulties from constituents causing color, and both color and gum are attacked appropriately. Motor fuels, and heavier distillates, including for instance such distillate material of a character including unseparated gasoline and kerosene, are thus favorably treated.

As an example: A naphtha having a mercaptan sulphur content 0.0111 and containing cracked constituents was treated by thorough incorporation of iron carbonyl in, amount taken substantially less than theoretically requisite for reaction with the sulphur, the temperature being raised to 450-650 F. Whereas the distillate originally had a copper dish gum test 85.2, the final sotreated distillate had a gum test of 17.1.

As another example: In a system involving a cracking coil and drum and first and second fractionating towers, a feed of iron carbonyl at a rate less than sufiicient to react the H28 and mercaptan sulphur was introduced at the upper portion of the first tower. Whereas the gasoline taken off from the system without any use of the iron carbonyl had a color 7, and copper dish gum 69.8, operating with the same conditions but introducing the iron carbonyl as aforedescribed, the gasoline color had lightened up to 18, and the gum was only 13.1.

As readily seen, such a result is particularly attractive to refiners and to users, and the convenience with which the treatment can be applied is of great advantage.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In the preparation of petroleum distillates, eliminating color therein by introducing into the distillate an amount of carbonyl substantially less than an amount suficient to remove mercaptans and hydrogen sulphide and then distilling off a light distillate fraction.

2. In the preparation of petroleum distillates, eliminating color and gum therein by introducing into the distillate an amount of carbonyl substantially less than an amount sufiicient to remove mercaptans and hydrogen sulphide and allowing the same to act at elevated temperature above that of steam and below the serious decomposition temperature of the distillate.

3.- In the preparation of petroleum distillates, estimating the sulphur content in the distillate, and eliminating gum by introducing into the distillate an amount of carbonyl calculated substantially less than the amount chemically equivi5 temperature lies between alent to the mercaptan sulphur and allowing the same to act at elevated temperature above that of steam and below the serious decomposition temperature of the distillate.

4. In the preparation of petroleum distillates, providing a distillate containing cracked material, estimating the sulphur content, and reducing constituents causing colored products, by subjecting the distillate to elevated temperature with an amount of iron carbonyl less than what would correspond to the amount required to react with the total sulphur.

5. The process set forth in claim 2 in which the carbonyl is iron carbonyl and the elevated 400 and 700 F. ROBERT E. BURK. 

